Dynamic Molecular Organization of Membranes

The results are of general interest for the design of liposomes with better uptake and retention of drugs. It has been shown that prolonged retention in vitro of, for example, vincristine is accompanied by improved retention in vivo [90]. 

Liposomes can even be used as microreactors. Until recently, the utility of this technique was limited by the fact that they could be used for only a relatively short time because of depletion of the reaction mixture. It has now been shown that liposomes of l-palmitoyl-2-oleoyl-sn-glycero-3-phosphochoHne (POPC) can be used as a semipermeable microreactor after treatment with sodium cholate. It has been demonstrated that this allows a biochemical reaction to take place inside the liposomes but not in the external medium. Such cholate-induced POPC bilayers can also be used to insert enzymes [91]. 

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The transition of a number of phospholipid chains from an ordered to a disordered state is of direct relevance to the state of the cell membrane - it is a characteristic parameter for each phospholipid. The dynamic molecular organization in vesicles and membranes has been described in detail [15] and is shown schematically in Figure 3.3. Using the thermodynamic DSC technique, changes in phase transition... 

Ashikawa, I., J.-J. Yin, W. K. Subczynski, T. Kouyama, J. S. Hyde, and A. Kusumi. 1994. Molecular organization and dynamics in bacteriorhodopsin-rich reconstituted membranes Discrimination of lipid environments by the oxygen transport parameter using a pulse ESR spin-labeling technique. Biochemistry 33 4947 1952. 

Cazacu, A., Pasc-Banu, A. and Barboiu, M. (2006) Molecular and supramolecular dynamics — a versatile tool for self organization of polymeric membranes systems. Macromolecular Symposia, 245—246, 435—438. 

At the mesoscopic scale, interactions between molecular components in membranes and catalyst layers control the self-organization into nanophase-segregated media, structural correlations, and adhesion properties of phase domains. Such complex processes can be studied by various theoretical tools and simulation techniques (e.g., by coarse-grained molecular dynamics simulations). Complex morphologies of the emerging media can be related to effective physicochemical properties that characterize transport and reaction at the macroscopic scale, using concepts from the theory of random heterogeneous media and percolation theory. 

In the field of biology, the effects of hydration on equilibrium protein structure and dynamics are fundamental to the relationship between structure and biological function [21-27]. In particular, the assessment of perturbation of liquid water structure and dynamics by hydrophilic and hydrophobic molecular surfaces is fundamental to the quantitative understanding of the stability and enzymatic activity of globular proteins and functions of membranes. Examples of structures that impose spatial restriction on water molecules include polymer gels, micelles, vesicles, and microemulsions. In the last three cases since the hydrophobic effect is the primary cause for the self-organization of these structures, obviously the configuration of water molecules near the hydrophilic-hydrophobic interfaces is of considerable relevance. 

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